Keyboard for telephone dialing utilizing impedance variation



April 21, 1970 1c. MOANIN 3,508,013

KEYBOARD FOR TELEPHONE DIALING UTILIZING IMPEDENCE VARIATION Filed July 28, 1967 2 Sheets-Sheet 1 FIG 1 r k A L 1 5L t K Kt 1 c0 D D REC LR] R2 R3 R4,

R1 R1R1R1R2 R1R3 R1R4 April 21, 1970 c. MQNIN 3,508,013

Filed July 28, 1967 2 Sheets-Sheet ,2

United States Patent Int. (:1. ri04m 1/26 US. Cl. 17990 7 Claims ABSTRACT OF THE DISCLOSURE A keyboard device for dialing by impedance variation in which the act of operating any key on the keyboard causes on the one hand the positioning of two resistances connected to respective rectifier elements poled in opposite directions on the line-wires and on the other hand the disconnection of the station from the circuit, the identification of the key depressed taking place at the exchange through two successive measurements of the line current, one with direct supply and the other with reverse supply corresponding to the two resistances connected in circuit, wherein the device includes vertical driving bars and horizontal driving bars, one key actuating a vertical driving bar and a horizontal driving bar, each bar closing one working contact and positioning one resistance.

This invention relates to a keyboard device for dialing by impedance variation.

The applicants French patent of Addition No. 89,316, entitled: Keyboard Dialing Device discloses such a keyboard device for dialing by impedance variation. In this device the act of operating any key on the keyboard causes, on the one hand, the positioning of two resistances on the line wires, and, on the other hand, the disconnection of the station from the circuit. Each resistance is connected in series with a diode, and the two dioderesistance groups are connected in parallel across the line wires, the diodes being oriented in reverse directions. In one step of operation only one resistance has the linecurrent passing through it; then the-current is reversed at the exchange and in the second step it is the second resistance that has the current passing through it. The combination of the two steps corresponds to the key depressed and the number of different combinations corresponds to the ten keys on the keyboard. The signalling system is therefore determined by the different values given to the two resistances constituting the two groups. So that there is no ambiguity in the steps, the values of the resistances must lie within certain limits; in fact each resistance-diode may assume, for example, only one of four values either in one direction or other of the current.

The present invention relates more particularly to a general electromechanical keyboard arrangement adapted to be applied to the device described in the abovementioned French patent application.

One of the objects of the invention is to provide a strong and economical keyboard.

The keyboard device according to the invention includes vertical driving bars and horizontal driving bars, one key actuating a vertical driving bar and a horizontal driving bar, each bar being adapted to close one working contact and position one resistance with respect to the lines.

According to one feature of the invention, the arrangement of the keys on the keyboard is such that the Figures 1, 2, 3, 4, 5, 6, 7, 8, 9, and 0 grouped in three rows of three keys and one row of one key situated in ice the middle column, extend from left to right and from top to bottom, the four rows corresponding to the four horizontal bars, each of which positions the resistances R to R respectively, and the three columns of the keyboard corresponding to the resistances R R and R respectively, only the key of numeral 9 having an individual contact and not acting on horizontal and vertical bars.

According to another feature of the invention, the keyboard arrangement in accordance with the invention may give the following code for the resistance combinations using resistances R R R and R corresponding to the ten figures of the keyboard:

R1 R3 R2 R2 1 4 3 3 1 2 3 4 2 3 1 1 2 4 4 4 According to yet another feature of the invention, the keyboard arrangement may be obtained by a permutation of the columns and/or the rows of the keyboard, the individual key being able to occupy any position.

According to a still further feature of the invention the keyboard arrangement may be obtained by systematically combining the four horizontal resistances and the four vertical resistances. One thus obtains a table of sixteen combinations, only ten of which are different, these being grouped in a triangle with a combination R R in the first column, two combinations R R and R R in the second column, three combinations R R R R and R R in the third column and four combina- IIIOIIS R1 R4, R2 R4, R3 R4 and R4 R4, in the fourth column, the arrangement of the keyboard being obtained by effecting the following permutations: The third column is placed in the first position, the fourth column is placed in the second position, the second column is placed in the third position, the first column with only one combination is treated as a particular case and placed at the bottom of the third position.

Other features of the invention will appear from the following description, given solely by way of example, of one embodiment of the device according to the invention shown in the accompanying drawings, in which:

FIGURE 1 shows a schematic diagram of the dialing circuit according to the above-mentioned French patent;

FIGURE 2 is a diagram to aid the comprehension of the operation of the device according to FIGURE 1;

FIGURE 3 shows the combinations of possible resistances according to the invention;

FIGURE 4 is one of the desired arrangements of the keyboard keys;

FIGURE 5 shows a triangular keyboard arrangement in relation to FIGURE 3;

FIGURE 6 shows the changeover from the triangular arrangement according to FIGURE 3 to the arrangement desired according to FIGURE 4;

FIGURE 7 shows the general electro-mechanical diagram of the keyboard according to the invention.

In the circuit shown in FIGURE 1, the subscribers line is represented by dotted lines L L The subscriber station is connected to the points A and B of the line while the exchange side is connected to the points A and B When any key of the keyboard is depressed, working contacts t and t are made and a normally closed contact r is broken after making of the contacts t and t. In a first stage of operation the current coming from the exchange passes through the contact t, a diode D and a resistance R; in a second stage of operation after reversal at the exchange, the current passes through the contact t, a diode D and a resistance R.

The combine receiver CO is in circuit when the keys of the keyboard are in the resting position. At the exchange, change-over contacts I and I cause the reversal of the supply to the subscriber; they are controlled by a receiving device REC. There are four resistance values for R and R; one thus has ten different combinations between R and R which correspond to the ten kays of the keyboard, as will be seen hereinafter.

FIGURE 2 serves to explain the role played by the resistances inserted in the line when a key is depressed; the axis Ox thereof is graduated in milliamperes, for example. When the receiver is replaced (interval CR), the intensity of the line current determined by the impedance varies from to 1' according to the extent of the latter. When dialing takes place and a resistance is inserted in the line, the intensity varies between two values according to the length of the line; for example, for the resistance R the line intensity may vary between i and i for the resistance R between i, and i etc. To each range of values such as i i corresponds the setting of a relay which thus detects the resistance R inserted; as two successive current steps are carried out, one direct and the other reversed, two relays are finally set olf which, according to a code, correspond to the figure whose key has been depressed and which is communicated to the recording device.

FIGURE 3 is a table showing in a known manner the various possible resistance combinations derived from resistances R R R and R The vertical column shows for example the values R to R, which may be assumed by the resistance R of FIGURE 1,, and the rows across give the values R and R; that can be assumed by the resistance R of FIGURE 1. One thus obtains sixteen combinations, of which those in the shaded part are duplicated, because the order of steps does not matter. There thus remain ten different combinations which may correspond to the ten figures of the keyboard. It will be noticed that there is one combination in the first column R R two combinations in the second column, R R and R R three combinations in the third column, R R R R and R R and four combinations in the fourth column, R R R R R R and R R the general form of the combinations used is that of a triangle.

FIGURE 4 shows a keyboard arrangement which it is desired to obtain; there are. four rows and three columns. In the first row are the figures 1, 2 and 3; in the second row, the figures 4, 5 and 6; in the third row there are the figures 7, 8 and 9 and in the fourth row, at the bottom of the middle column, the figure 0. The general form of the combinations is thus very different from the triangular form of FIGURE 3.

If one takes FIGURE 3 again, placing the keys corresponding to the combinations, FIGURE 5 is obtained; there is one column with one key associated with the resistance R a column with two keys associated with the resistance R a column with three keys associated with the resistance R and a column with four keys associated with the resistance R it is the same for each horizontal row but a row of four keys is associated with the resistance R a row of three keys with the resistance R etc. The known triangular arrangement is thus obtained.

FIGURE 6 shows how one obtains the desired keyboard arrangement given in FIGURE 4, starting from FIGURE 5. According to the invention the third column of FIG- URE 5 is placed in the first position, the fourth column in the second position and the second column in the third position; the first column with a single key is treated as a particular case: The corresponding key is placed below the two key column and is provided with an individual contact. It will be seen that a unique association of two resistances R and R corresponds to each key of the keyboard, the first controlled by the horizontal bar R and 4 the second controlled by the vertical bar R The following code results for the ten figures of the keyboard.

R1 R3 2 2 2 R R (7) 4 3 (3) R R 3 4 R2 R3 1 1 5 R R. 4 4

FIGURE 7 is the e-lectro-mechnnical diagram of the keyboard according to the invention. The keyboard comprises horizontal bars H H H and H and vertical bars V V and V which may be spring loaded in the wellknown manner. Each key 1, 2, 3, 4, 5, 6, 7, 8, 0 controls movement of a vertical bar and a horizontal bar, each vertical bar closing a respective contact t t t and each horizontal bar closing a respective contact t' t t t'.,. The horizontal bars may be positioned above the vertical bars, as seen in the figure, or vise versa, with the key stems (not shown) engaging the bars to effect longitudinal movement thereof upon depression of a key to close a corresponding switch. As each contact closes, it connects a resistance R R R or R in the line. Only the key 9 has an individual contact t The line A is likewise connected to the contact t through a resistance R to the contact t through a resistance R to the contact t' through a resistance R to the contact t through a resistance R The line B on the other hand is connected to the contacts t t 2' t' mounted in parallel through a diode D, and to the contacts 1 t t mounted in parallel through a diode D. When any key, 5 for example, is depressed, the two bars H V which are at its intersection are displaced, the horizontal bar H makes the contact t and the vertical bar V makes the contact I.;, the contact r being broken after the two contacts 1' and L, are made.

If one supposes direct supply with positive polarity at A and negative polarity at B, it will be seen that the circuit is made as follows: Wire A, resistance R contact t diode D and wire B for the first step of operation; as the second step of operation takes place after reversal of the line current, that is to say with positive polarity at B and negative polarity at A, the circuit is made via: Wire B, diode D, contact t resistance R and wire A.

There is a particular case for the key 9 which comprises an individual contact 1 if the positive polarity is at A the circuit closes through: Wire A, horizontal resistance R contact t and wire B. In spite of the fact that this circuit does not have a diode, there is no ambiguity because t is the only contact made. If the positive polarity is at B the circuit is closed through: Wire B, contact t horizontal resistance R and wire A. It will be seen that in this particular case, the same measuring circuit is maintained before and after reversal of the supply.

The resting contract r is in a known manner actuated by the group of horizontal bars and by the key 9; this contact is opened after closing of the working contacts and has 'as its function to put the receiver out of circuit during the operation of a key.

It is obvious that the invention is by no means limited to the embodiments described and illustrated which have been given merely by way of example; in particular without going beyond the scope of the invention, certain arrangements could be modified or certain means could be replaced by equivalent means.

In particular, the individual key may occupy another position on the keyboard; for example, if may be placed in another column or in another row. The invention is not limited to the permutation given by way of example above; any other permutation may be used. For example, i

the second column may be placed in the first position, the fourth column in the second position, the third column in the third position, the individual key being placed at the bottom or at the top of the second column in the first position. In the permutations the fourth column is preferably placed in the middle.

I have shown and described several embodiments in accordance with the present invention. It is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to a person skilled in the art and I, therefore, do not wish to be limited to the details shown and described herein, but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

I claim:

1. A keyboard device for dialing by impedance variation in which the act of operating any key on the keyboard causes on the one hand the positioning of two resistances connected to respective rectifier elements poled in opposite directions across first and second line-wires and on the other hand the disconnection of the station from the circuit, the identification of the key depressed taking place at the exchange through two successive measurements of the line current, one with direct supply voltage of one polarity and the other with reverse polarity supply voltage, corresponding to the two resistances connected in circuit, wherein the device comprises:

a plurality of keys each representing a unique symbol designation,

a plurality of spaced vertical driving bars and spaced horizontal driving bars capable of displacement by certain ones of said keys, substantially each key actuating a unique pair of said driving bars including one vertical and one horizontal bar,

a switch associated with each driving bar having contacts which are closed by displacement of the associated driving bar, and

a plurality of resistances of different value connected in series with a rectifier device, each driving bar serving to connect one resistance across the line wires upon actuation of the switch associated therewith.

2. A device as claimed in claim 1 wherein said keys are provided as a ten key arrangement in three columns and four rows, one key being independent in one row, a combination of two resistances of finite values corresponding to each symbol.

3. A device as claimed in claim 2, wherein the device includes four horizontal bars and three vertical bars controlled by nine keys 1, 2, 3, 4, 5,, 6, 7, 8, and 0, the key 9 having an individual working contact, each horizontal and vertical bar acting on only one switch contact and connecting one resistance across the line, four resistances being associated with the horizontal bars and three resistances with the vertical bars, but only four different resistance values being used.

4. A device as claimed in claim 3, wherein the keys 1, 2 and 3, control horizontally a first resistance R the keys 4, 5 and 6, a second resistance R the keys 7 and 8, a third resistance r the key 0 a fourth resistance R and vertically the keys 1, 4 and 7 control a third resistance R the keys 2, 5, 8 and 0, a fourth resistance R the keys 3 and 6 a second resistance R the key 9 controlling individually a first resistance R 5. A device as claimed in claim 4, wherein in the keyboard arrangement the following code is obtained:

Figure 1Combination R R Figure 2Combination R R Figure 3Combination R R Figure 4-Combination R R Figure 5Combination R R Figure 6-Combination R R Figure 7-Combination R R Figure 8Combination R R Figure 9Combination R R Figure 0-Combination R R in each combination the first resistance corresponding to the control of the horizontal bar and the second resistance to the control of the vertical bar.

6. A device as claimed in claim 2, wherein the keyboard arrangement is obtained by a permutation of the columns and rows of driving bars of the keyboard.

7. A device as claimed in claim 6, wherein the keyboard arrangement is obtained by systematically combining the four horizontal resistances and the four vertical resistances, thus obtaining a table of sixteen combinations, ten different combinations of which being assigned to the indivdiual keys, these being grouped in a triangle with a combination R R in a first vertical line, two combinations R R and R R in a second vertical line, three combinations R R R R and R R in a third vertical line and four combinations R R R R R R and R R in a fourth vertical line, the arrangement of the keyboard being obtained by effecting the following permutations:

the third vertical line is placed as the first column,

the fourth vertical line is placed as the second column,

the second vertical line is placed as the third column,

the first vertical line with only one combination is treated as a particular case and placed at the bottom of the third column.

References Cited UNITED STATES PATENTS 2,927,971 3/1960 Busala "179-90 KATHLEEN H. CLAFFY, Primary Examiner T. J. DAMICO, Assistant Examiner 

